The objective of this program is the development of a new finger joint prosthesis. The new prosthesis employs a mechanical hinge to provide flexure, and it incorporates a mechanical stop to prevent hyperextension. It is composed of titanium alloy and uses a bearing surface made from ultra high molecular weight polyethylene. The metal stems of the implant are integrally textured so that it may be implanted without the use of bone cement. Bone attachment to this surface will also better distribute loading from the joint to prevent bone erosion. The hinge mechanism is covered with an elastomeric jacket which employs a microporous silicone rubber surface designed to promote soft tissue attachment to its surface. This tissue attachment has been shown to lessen fibrous tissue encapsulation of the joint by preventing relative motion of tissue in contact with the implant during joint movement. The jacket, analogous to a synovial membrane, also isolates the hinge from infiltration by connective tissue and contains within it any wear products from the joint mechanism. Currently elastomeric joint spacer prostheses are used for joint replacement surgery. these prostheses have a high incidence of mechanical failure. They also provide limited functionality, and frequently show a progressive loss in range of motion with time. The new prosthesis has the potential for improved mechanical reliability and functionality, while the reduction of scar tissue formation around the implant is likely to preserve its useful range of motion.